cmd/gocyclo: remove meaningless -total and -total-short options

Fixes #47

Don't skip directories `.` and `..`. Fixes #44

CHANGELOG: update for version 0.5.0

update CHANGELOG for v0.4.0

Update CHANGELOG.md for v0.3.1

Export the AnalyzeASTFile function

README: Add pkg.go.dev and Go report card badges

add go.mod file